Physics Letters B (Oct 2015)

Photoproduction of ω mesons off the proton

  • A. Wilson,
  • V. Crede,
  • A.V. Anisovich,
  • J.C.S. Bacelar,
  • B. Bantes,
  • O. Bartholomy,
  • D. Bayadilov,
  • R. Beck,
  • Y.A. Beloglazov,
  • K.T. Brinkmann,
  • R. Castelijns,
  • H. Dutz,
  • D. Elsner,
  • R. Ewald,
  • F. Frommberger,
  • M. Fuchs,
  • Chr. Funke,
  • R. Gregor,
  • A. Gridnev,
  • E. Gutz,
  • J. Hannappel,
  • W. Hillert,
  • P. Hoffmeister,
  • I. Horn,
  • I. Jaegle,
  • T. Jude,
  • J. Junkersfeld,
  • H. Kalinowsky,
  • V. Kleber,
  • Frank Klein,
  • Friedrich Klein,
  • E. Klempt,
  • M. Kotulla,
  • B. Krusche,
  • M. Lang,
  • H. Löhner,
  • I.V. Lopatin,
  • S. Lugert,
  • T. Mertens,
  • J.G. Messchendorp,
  • V. Metag,
  • M. Nanova,
  • V.A. Nikonov,
  • D. Novinski,
  • R. Novotny,
  • M. Ostrick,
  • L.M. Pant,
  • H. van Pee,
  • M. Pfeiffer,
  • A. Roy,
  • A.V. Sarantsev,
  • C. Schmidt,
  • H. Schmieden,
  • S. Shende,
  • V. Sokhoyan,
  • N. Sparks,
  • A. Süle,
  • V.V. Sumachev,
  • T. Szczepanek,
  • U. Thoma,
  • D. Trnka,
  • R. Varma,
  • D. Walther,
  • Ch. Wendel,
  • U. Wiedner

DOI
https://doi.org/10.1016/j.physletb.2015.08.011
Journal volume & issue
Vol. 749, no. C
pp. 407 – 413

Abstract

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The differential cross sections and unpolarized spin-density matrix elements for the reaction γp→pω were measured using the CBELSA/TAPS experiment for initial photon energies ranging from the reaction threshold to 2.5 GeV. These observables were measured from the radiative decay of the ω meson, ω→π0γ. The cross sections cover the full angular range and show the full extent of the t-channel forward rise. The overall shape of the angular distributions in the differential cross sections and unpolarized spin-density matrix elements are in fair agreement with previous data. In addition, for the first time, a beam of linearly-polarized tagged photons in the energy range from 1150 MeV to 1650 MeV was used to extract polarized spin-density matrix elements. These data were included in the Bonn–Gatchina partial wave analysis (PWA). The dominant contribution to ω photoproduction near threshold was found to be the 3/2+ partial wave, which is primarily due to the sub-threshold N(1720)3/2+ resonance. At higher energies, pomeron-exchange was found to dominate whereas π-exchange remained small. These t-channel contributions as well as further contributions from nucleon resonances were necessary to describe the entire dataset: the 1/2−, 3/2−, and 5/2+ partial waves were also found to contribute significantly.

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